1. Field of the Invention
This invention relates to the formation of a field implant channel stop region and to a semiconductor device with a field implant channel stop region. The field implant channel stop region is formed without using additional masks or masking steps by using either a large angle tilted ion implantation beam or a higher energy normally directed ion implant beam.
2. Description of Related Art
In the formation of large scale integrated circuits using field effect transistors isolation between devices is of critical importance. The formation of a field oxide isolation region has been used for some time to provide isolation between devices. As isolation requirements become more severe a local increase in doping level to form a channel stop region has been used for improved isolation. Conventional methods of forming a channel stop region, however, require the use of an extra mask and extra masking steps. This invention forms the channel stop region without the use of an extra mask or extra masking steps by using either a large angle tilted ion implantation beam or a higher energy normally directed ion implant beam.
U.S. Pat. No. 5,240,874 to Roberts; U.S. Pat. No. 4,987,093 to Teng et al; U.S. Pat. No. 5,116,775 to Katto et al; and 5,004,701 to Motokawa show ion implantation after the formation of the field oxide for the formation of a channel stop. U.S. Pat. No. 5,290,718 to Fearon et al and U.S. Pat. No. 5,019,520 to Komori et al show ion implantation after the formation of the field oxide to adjust the channel threshold.